This invention is in the field of .beta.-alanine. More specifically, this invention is directed to a process for preparing pure or substantially pure .beta.-alanine.
In the prior art amino acids have been prepared by: (a) hydrolyzing the corresponding nitrile with an aqueous alkaline earth metal hydroxide to form an alkaline earth metal salt of the amino acid; and (b) treating the alkaline earth metal salt with carbon dioxide to form the free amino acid (which remains in solution) and an alkaline earth metal carbonate (which precipitates). The amino acid is then recovered. This method, as applied to the preparation of .beta.-alanine, is taught by "Organic Syntheses", collective volume 3, pp. 34-36, John Wiley and Sons, Inc., 1955.
It is desirable to replace the alkaline earth metal hydroxide of the prior art with sodium hydroxide because the latter has a lower equivalent weight than strontium and barium hydroxides, is more soluble, is easier to handle under plant conditions, and the ions of sodium, unlike those of barium, (a preferred alkaline earth metal hydroxide) are not toxic. However, such substitution introduces a complication in the separation and recovery of the amino acid (.beta.-alanine) because sodium carbonate, unlike the alkaline earth metal carbonates, is readily soluble in water, thereby to render to separation and recovery of pure or substantially pure .beta.-alanine difficult.
A method for separating certain free amino acids from a system comprising the amino acid, sodium chloride, and water is taught by U.S. Pat. No. 3,433,832 (Swanson et al, 260/534).
The Swanson et al method is not applicable to amino acids such as .beta.-alanine which have a solubility greater than 35.0 parts per 100 parts of water at 100.degree.C. The process of our invention has been found to present an effective and convenient method for recovering .beta.-alanine from a system consisting essentially of water, .beta.-alanine, and sodium chloride. Such a system results where the amino acid (.beta.-alanine) is formed from the corresponding nitrile by hydrolysis with sodium hydroxide followed by treatment with hydrochloric acid to convert the intermediate sodium salt (sodium .beta.-alaninate (sodium .beta.-aminopropionate)) to the free amino acid (.beta.-alanine).